First-Principles Investigation On New Magnetic Materials Containing Transition Metals

In recent years,spintronics devices and materials are an emerging research field.Due to the potential application value in the field of magnetic storage and spin injection,researchers are increasingly interested in the research of spintronics materials.Semi-metallic materials are a potential spintronics material.The upward and downward orbits of the metal spin pass the Fermi level,and both directions have100%spin polarization;the upward and downward orbits of the spin of the insulator do not pass the Fermi level,and the width of the band gap formed between the top of the valence band and the bottom of the conduction band mostly exceeds a certain value.The semi-metal is very different from the above two materials.One of the spin-direction electron orbits passes through the Fermi level and then exhibits metal properties,and the other spin-direction orbit has a certain width of the band gap,and displays the semiconductor properties.This structure also has a spin polarizability of100%,compared with traditional magnetic alloy materials,materials with such energy band structures are considered to be a new type of magnetic materials.The research in this paper shows that a quaternary Heusler alloy doped with transition metal(Ti)can form a new type of spin-gap-free semimetal material;Si-based and Ge-based alloys doped with transition metal(TM)can also form a DMH Semi-metallic materials.The electrical and magnetic properties of these two types of materials were analyzed in detail.The main conclusions are as follows.(1)The first-principles calculations were used to analyze the electrical and magnetic properties of Ti atom-doped spin gapless semiconductor quaternary Heusler alloy Ti₂Co Si.When 1/4 of C_Oatoms are replaced by Ti atoms,a new type of spin gapless semi metallic material can be obtained.At the same time,using first-principles calculations we investigated properties of the replacement of Ti_2.25Co_0.75Si alloy with boron(B),aluminum(Al),gallium(Ga),phosphorus(P),arsenic(As),and antimony(Sb)Si element.Results confirmed that Ti_2.25Co_0.75Si_0.5B_0.5Ti_2.25Co_0.75Si_0.5Al_0.5and Ti_2.25Co_0.75Si_0.5Ga_0.5are semi-metal ferromagnetic materials Ti_2.25Co_0.75Si_0.5P_0.5,Ti_2.25Co_0.75Si_0.5As_0.5,and Ti_2.25Co_0.75Si_0.5Sb_0.5are spin-band-free semiconductor materials.(2)The electronic structure and magnetic properties of the ground-state Si atoms doped with 3d and 4d transition metals(TM)were studied.The doping methods are interstitial sites and substitution sites,respectively.Some 3d and 4d transition metal(TM)-doped semiconductor silicon has relatively strong magnetic properties and has 100%spin polarizability near the Fermi surface.Among them,alloys formed by Fe,Zr,Nb,Mo instead of doped silicon show semi-metallic properties,and alloys formed by doping other metals have metallic properties.The calculation results also show that 3d transition metal(TM)doped Si-based compounds are more magnetic than 4d transition metal(TM)doped Si-based compounds.These alloys can reflect their application value in the fields of magnetocaloric and magnetoelectricity.(3)The electronic structure and magnetic properties of 3d and 4d transition metals(TM)doped with ground-state Ge atoms through alternative methods were studied.The doped transition metal has a certain magnetic property.The DMH obtained by doping has a certain magnetic property due to the electron spin transition,in which the transition metal d orbitals and adjacent silicon atom p orbitals are hybridized to some extent.In the end,the two spin directions form different electron densities,thus exhibit certain magnetic properties.The conclusion is the magnetic properties of the Ge-based alloys doped by 3d transition metals are greater than the magnetic properties of the Ge-based alloys doped by 4d transition metals.